Electrical resistance furnace.



H. HELBERGER. ELECTRICAL RESISTANCE PURNACE.

APPLICATION FILED AUG. '11, 1911.

Patented Aplfs 16, 1912.

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H. HELBERGBR. ELECTRICAL RESISTANCE EUENAGE.

APPLICATION FILED AUG. l1, 1911.

Patented Apr. 16, 1912.

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awww/Coz WHA/www *www HUGO HELBERGER, OF MUNICH, GERMANY.L

ELECTRICAL RESISTANCE FURNACE.

Specification of Letters Patent.

Patented Apr. 16,1912.

Application filed August 11,'1911. Serial No. 643,564.

To all whom it may concern:

Bc it known that I, Hioo Hnnnncnn, a subject ot' the Emperor ot' Germany, residing at Munich, (.irermany, have invented certain new and useful Improvements in Elec trical Resistance Furnaces; and l' do hereby declare the following to he a full, clear7 and exact description of the same7 reference being had to the accompanying drawings, forming a part of this specification, and to the figures and letters of reference marked thereon.

Thepresent invention relates to improvements in'that type of electrical furnaces in which the heat is produced by the passage of an electric current through a portion ot the wall of the furnace'.

The invention relates more especially to turnaces of said type in which the current is caused to flow in the wall ot the turnace iii a direction parallel with the aXis of the turnace, the objects ot the invention being to provide a furnace particularly adapted for melting purposes in which the heat generated will be conserved and utilized to the best possible advantage, and with which the charging and discharging may he etl'ectcd in the most convenient manner.

A further object ot the invention 'is to prgvide a furnace ot' t-he type mentioned, in which the surfaces ot the heating wall will be. protected against oxidation during the operation ot the furnace. 'whereby the life ot said wall will be greatly prolonged.

Referring to the accompanying drawl niger-Figure 1 is asectional elevation7 more or less diagramn'iatic in character, illustrating a simple embodiment ot a furnace constructed in accordance with the present inrveiitioii; Figs. 2 and 3 are similar views, showing a `furnace asseliihle l.\vit.h the nicchanism 'toi' lilting or discharging the molten material theret'ron'u and means tor controlling such discharging mechanism; lFig. -lis a detail view showing the heating wall ot the furnace provided with intermediate contacts, whereby the structure is adapted. tor use in connection with a three-wire source ot current; Fig, 5 is a perspective view ot another arrangement or construction ot the heating wall oi the t'iirn'ace adapted tor a system ojf coiuliictors having more than two poles; and Fig. G is a view corresponding closely-to Fig. l. but with the heating wall 'torined in sections and ar- 'ranged for application thereto of current from a number ot terminals whereby the heater may he divided into zones, each heated hy its own branch of the current so as to afford an opportunity for regulating the heat at different points.

`Like letters ot' reference in the several figures indicate the same parts. y

The furnace of the present invention consists primarily of a heating cylinder or tube H in Figs. l, 2 and 3, `formed of carbon, graphite clay, graphite or like material, which, as well known, may he heated to a high temperature by the passage therethrough of an electric current ot proper ainperage. This heating cylinder is adapted to have the current supplied thereto in a number of different ways which will be hereinafter referred to, but in all instances it is yn'eterred that the current should iiow in the heating wall in a direction parallel with the y axis Aot the cylinder and the cylinder is usually arranged in a vertical position, as shown in the drawings.

lVithin the cylinder there is removably located a lining or melting crucible T which is ot highly refractory material, and made to lit as accurately as possible within the heat.- ing cylii'ider`r so as to thoroughly protecti the inner tace ot' the cylinder against oxidation Since, however, it is not possible to make them tit absolutely tight, and thus completely prevent any oxidation ot the heat-ing cylinder.y and 'since it is desirable to have intimate contact between the walls in order to secure the best possible conditions for the transmission ot heat by conduction, it. is preferred to make the lining or crucible, ot" material which heconies soii'icwhat soft when heatedI to a very high temperature. Practically all clay has this property and when the Crucible is madoot clay it is only necessary to raise th(` hea t ol a. filled crucihle to a point where the wall becomes slightly plastic in order that the contents ot the Crucible may torce its wall outwardly and firmly against the heatingl cylinder. This will result in a tight titboing obtained and may loe successfully used lor ten'iperatures up to 18000. The critical temperature at which the clay becomes sligl'itly plastic may he recognized when white silicic acid vapors are given od.

For higher temperatures than 1800i). linings ot metal cxids, such as magnesia, Zirconium oxid or the like are used. and are either prl fd within the heating cylinder with a binding material, such as boraeic acid.' tai' o1' the like` or, as preferred. arc formed without binding material in the following manner :Wtfrucible-lihe vessels of thin sheet metal. are placed in the heating` cylinder, leaving a space between them and the cylinder. ln this space the finely pulverized metal oxids are talnped without binding material of any ltind. rlhe sheet metal vessel supports this lining as long as the heatingl cylinder is cool. butl melts when a white heat is reached, but at this heat the metal oxids siuter and form a conipletely solid melting Crucible. rThe crucible, so formed. is, however, not united to the heating cylinder. but can be easily pushed up out of the same by the lifting apparatus to be presently descril'aal.

The crucible and lining are designed to protect thel interior wall of the heating cylinder from oxidation and to further conserve the heat, a ren'iovablc cover D is pro- Lvided at the top. and at the. bottom there is provided the upper end of a lifting mechanism, upon which the lining or Crucible may rest, and in some instances said lifting mechanism may constitute a support for the heating cylinder itself. As illustrated the lifting mechanism in the form of a plunger indicated by the reference letters T/L,

which is supported in line with the lining or crucible T and is adapted to be forced upwardly by hydraulic or other power illustrated in Figs. Q and 3 of the accompanying drawings, although other known means may be employed. The upper end of the lifting mechanism is of such character that. when it'forces or lifts the lining or Crucible up out of the heating cylinder it will itself closel the cylinder against the admission of air, thereby protecting the inner face of the heating cylinder against oxidation, when the lining or crucible is not present. As shown in Fig. l, the lifting mechanism may be provided with a flange A which by env ga gement with the lower end of the heating cylinder may be made to lift the cylinder itself out of its surrounding casing.

rIhe entire heating tube or' cylinder is surrounded by refractory non-heat conducting material M, preferably of metal oXids or similar materials, so that there can be no contact of the heating cylinder with thc atmospheric air, whereby oxidation on the exterior surface is prevented.

there the heating cylinder is adapted to be lifted it should be embedded in a substance, such, for example, as magnesia,

. which sinters and hardens under heat, thereby forming a solid, but thin, casing around the heating cylinder, which casing will stand when the cylinder is removed, and be ready for the reception of a new cylinder, thus avoiding the laborious building up and filling in of the insulating material whenever a new cylinder. is to be supplied.

The heating cylinder itself, as before stated, preferably consists of carbon, graphite clay, lgraphite or similar materials, such as are generally. used, and it is differently shaped according to the kind of current employed, but the -direction of the current is always parallel to the axis of the cylinder.

In Fig. l the simplest form of heating cylinder is illustrated, and is adapted for the connection of a twopole source of current; P and P2 indicatingr the contact terminals for the heating tube, said contact terminals conveniently being of annularform.

In the construction shown in Fig. 4, the heating cylinder is adapted for connection with a three-wire source of current, for eX- ample, a rectified current. In this instance,l the' heating cylinder is made in a single piece, but is provided with two projecting ribs R and R adapted to carry the contact terminals P3 and P4, said contact terminals being in addition to the end terminals P and P2, which correspond to those herein before referred to.

The construction illustrated in Fig. t is primarily adapted for a heating cylinder, made of one piece and of relatively small size, but when the cylinder is of large dimension, it becomes desirable to form it in sections, for instance, as illustrated in Fig. (3. In this case the heating cylinder consists of three separate parts a, 7), c, which are held by means of the pole pieces P, P3 and P4, and together with said pole pieces are firmly clamped by the rods S72 and S79 having thumb nuts or adjustable fastenings F, F', at the ends. Tht` whole structure is rigid and the three sections a., 7), c, form three Zones which may be heated to different dcgrecs by regulation of the current fed to each section'. This is an important advantage in electric Crucible heating, since it is often desirable to be able to maintain the greatest heat atl a certain zone. either at the top, the bottom or at the middle.

The cylindrical form of the heating tube or cylinder may be maintained, and the current caused to flow in the walls of the same, parallel with the axis of the cylinder. by making the walls discontinuous transversely of the axis, for instance, as illustrated in Fig. 5. Inthis construction, the cylinder is provided with three or more slots V which divide the tube into practically equal parts, the slots extending in from one end of the cylinder but leaving the opposite end integral for the passage of currentY from one section to the other. The number of parts or sections determines the number of terminals which must be provided for supplying current, and as illustrated, three sections and terminals R', R2, R3, are provided, but it will be understood that.v the cylinder may be similarly subdivided into amy desired' number of sections or segments which at one end are electrically connected and held together by a common union. The spaces or slots between the sections are tilled with highly refractory insulating material, and in this, as well as in the other forms of heater illustrated it will be understood that in use theexterior of the cylinder is inclosed by highly refractory heat insulating material, impervious to air, such as lime, magnesia, infusorial earth or like material, and that the lining or Crucible within the cylinder, together' with the cover and lifting mechanism completely protect the inner face of the cylinder against oxidation.

By providing a liftmg mechanism in connection with the furnace, it will be understood that diilicult-ies and expense incident to the repacking of the insulating material around, the furnace when a new heat-ing cyl inder has to be substituted, are to a large extent avoided, for with the lifting mechanism, not only may the crucible be removed from the cylinder, andthe cylinder-guarded against the entry of atmospheric air, butl the cylinder itself may be lifted, leaving the in sulating material standing in place ready for the reception of a new cylinder.

It is further to be understood that while I have above described and illustrated certain arrangements embodying my invention that it is n ot limited to these specifically but may be carried out in many ways that will. occur to those skilled in the art. y

Having thus described my invention, what I claim as new and desire to secure by Letters Patent. of the United States, is:

1. ln an electric furnace, the combination with the cylindrical heating chamber adapt ed to be heated by the passage of an electric current through it, of a removable lining mounted in said cylinder with its exterior face in contactwith theinterior face of the cylinder, whereby oxidation of the latter vis prevented, and la. refractory heat insulating inclosure surrounding the outer wall of said cylinder, whereby oxidation of its outer face and radiation of hea-t therefrom are prevented.

2. In an electrical resistance furnace, the combination with the heating cylinder ha ving circuit terminals connected therewith and heat insulating material inclosing said cylinder, of a removable lining for the cylinder formed of material having the property of becoming soft at high temperature, and means associated. with said heating cylinder for removing said liningl and protecting tht` inner face of the cylinder against oxidation when the lining is removed.

3. In an electrical resista-nce furnace, the combination with the heating cylinder opt-n at top and bottom, of a removable cruciblo mounted within said cylinder with its outer face in contact with the inner face ofthe cylinder, whereby oxidation of the latter lis prevented, a lifting mechanism for supportingsaid crucible within the cylinder, and a cover of refractory material for closing the upper end of the cylinder.

4. In an electrical resistance furnace, the combination with the heater formed by a cylindrical bodyA open at top and bottom adapted to be heated by the passage of an electric current therethrough, and circuit terminals engaging said cylindrical body, of anvinclosure of heat insulating refractory material surrounding said cylindrical body, a crucible mounted within the heaterand with its outer face in position to protect the inner face of the cylinder against oxidation, a crucible lift-ing mechanism movable into and out of the lower end of the rheater for supporting the Crucible within the cylinder and lifting it up out of the cylinder, and

means for closing the upper end of the heater.

5. In an electrical resistance furnace, the combination with the heater formed by a cylindrical body having annular circuit terminals coperatng therewith at different points longitudinally of the axis'of the cylinder for supplying heating current to the cylinder, of a removable Crucible mounted within and in intimate contact withthe inner face of the heater, whereby oxidation of said face is prevented, and means for lifting said Crucible, movable into and out of the lower end of the heater.

G. In an electrical resistance furnace, the combination with a heater formed of mate rial adapted to be heated by the passage therethrough of an electric current, of circuit terminals coperating with the ends of said heater, and an annular circuit terminal surrounding said heater intermediate theA ends whereby the heater may be divided into zones transversely of its axis, each of which zones may be heated to a different de gree fromthe other.

7. In an electrical resistance furnace, the combination with a cylindrical heater `formed of material adapted to be heated by the passage therethrough of an electric current, of circuit terminals cooperating with the ends of said cylindrical heater, and a plurality of circuit terminals surrounding Yand cooperating with said heater, intermediate the ends, whereby current. may be supplied for heating the heater in Zones transversely of its axis.

`8. ln an electrical resistance furnace, the combination with a cylindrical heater' forn'ied in sections longitudinally of its axis, and annular circuit terminals cooperating with theI ends of-each of said sections, whereby the heater is sub-divided into'zones each of which may be heated di tferently from the other.

9. ln an electrl -al resistance furnace, the combination with the heater formed by a lio evlinilrieal ho ly open :it lop und bottoni l the healer for supporling lhe erueihle withudnpted to he heated by the passage oi :in j in the healer und lifting it up out of the cyleleel'rie current ilnrel'hrough, und circuit inder, sziill plunger adaplecl to Close the Cylterniinnls engaging Suid eylindrieirl body, iuder at the upper end when lhuerneihle iS of :ui inelcsnre of heut insulating refractory forced out :igniusl the admission of air. material surrounding Sfiid e lindricail bod Y 1 u Crucible mounfeduwithin )lhe heater zml HUGO HELBIQRGEL with itsV outer face in intimate Contact with lVitnesses: the inner face of the cylinder, and :i plunger ARTHUR V. lV. Ce'rmn, l0 movable into and out of the lower enfl of MATHILDE K. HELD. 

